A power surge that caused a widespread blackout in Spain and Portugal was the most severe in Europe in the last 20 years, and the first of its kind, a report has found.
Damian Cortinas, president of the association of electricity grid operators Entso-e, said the incident was the first known blackout to be caused by overvoltage, which occurs when there is too much electrical voltage in a network.
This is new territory, Cortinas said, adding the role of Entso-e was not to apportion blame to any party over the cause.
April's outage caused significant disruption for nearly a day when it plunged areas into darkness, cutting internet and telephone connections and halting transport links.
The blackout affected large parts of Spain and Portugal, and briefly affected southwestern France.
The report, released on Friday, focused on the condition of the power systems on the day of the outage and the sequence of events leading up to it.
A series of cascading overvoltages—an increase in the electrical supply voltage above the established norm—was behind the outage, it concluded.
According to the report, automatic defence plans were activated but could not prevent the power system shutting down. It follows several separate investigations and reports by the Spanish government, as well as power and grid companies. The national energy watchdog and Spanish lawmakers are also conducting separate investigations.
Sara Aagesen, minister for ecological transition, said it was completely in line with the results of an investigation it commissioned which concluded in June that both the national grid provider Red Eléctrica and private electricity companies were at fault.
The outage triggered a broader debate that spilled into the political arena about Spain's energy model. The opposition suggested an increasingly heavy reliance on renewable energy could have been a factor in causing the blackout.
Emergency workers were called to 286 buildings to free people trapped inside elevators in the Madrid region, while hospitals implemented emergency plans, halting routine procedures. The incident has underscored the challenges within the energy sector as further investigations continue.
